U.S. Pat. No. 4,820,534 discloses a method for fixing labile substances such as, for example, essential oils in an extruded glass, characterised in that the quantitatively more important component present in a proportion by weight of at least 70% is a maltodextrin having a DE (dextrose equivalent) of up to 20. The resulting matrix is a hard, non-hygroscopic glass from which encapsulated essential oils or other aromas can be prepared without the addition of emulsifiers and flow promoting agents. In order to obtain small particle sizes, in particular particles smaller than 1 mm, coarse strands must first be prepared which are subsequently comminuted and sieved in a labour-intensive process, as a result of which undesirable dusty fines arise. A direct processing of this glass by way of perforated disks having small openings (smaller than 1 mm) is not possible because, at the necessary temperatures, undesirable aroma losses and aroma reactions, as well as carbonisation and blockages in the extruder, would result.
U.S. Pat. No. 5,972,395 discloses the use of a quantitatively subordinate proportion by weight, of from 15 to 30%, of the maltodextrin having a dextrose equivalent of up to 20. The encapsulation of water-insoluble lipophilic fish oil or of solid labile components such as carotene and maltol is described. These materials have only a slight plasticising effect on the matrix. This method cannot, however, be applied to the encapsulation of commercial aromas because practically all natural, nature-identical or artificial aromas contain components which act as highly effective plasticisers of the carbohydrate matrix according to U.S. Pat. No. 5,972,395, as a result of which the glass becomes sticky and difficult to process.
Very hard glasses make processing difficult on account of their high melt viscosity, such that flow through small openings is no longer possible. Soft matrices are impossible, or difficult, to process by way of melt extrusion and integrated comminution because the melt is too soft and the particles formed tend to adhere. This problem occurs in particular when the melt is discharged through small openings. In addition, soft glasses can result in undesirably large drops of the aroma in the matrix and hence even in efflux of the aroma in liquid form.
Carbohydrate matrices and processes for the preparation thereof are therefore sought which enable aromas to be encapsulated in a stable manner by means of melt extrusion and die-face pelletisation, while not having the disadvantages of the prior art which have been described. In the present invention, die-face pelletisation is understood to be a comminution, directly at the extruder exit, of the melt discharged from the extruder. The still soft surface structure is sealed by the action of the die-face pelletisation.